Blood vessel disease is a significant cause of premature disability and death. Heart attacks, strokes and other ailments are often caused by blood vessel disease.
The most common disease of the blood vessels is atherosclerosis. Atherosclerosis involves the accumulation of plaques of cholesterol, lipids and cellular debris within an artery. As the plaque accumulates, the artery wall thickens thereby narrowing the lumen of the artery. As the lumen narrows, the blood flow to tissue nourished by the artery is diminished. The development of plaques can also contribute to the formation of emboli or thrombi. An embolus is a moving obstruction such as a platelet aggregate. A thrombus can be a fixed obstruction such as a wall adherent blood clot or can become an embolus. A thrombus or embolus within a coronary artery can occlude the artery thereby causing myocardial infarction, angina and other conditions. A blockage caused by a thrombus or embolus within a vessel supplying blood to the brain can lead to a stroke. Renal, peripheral, and other blood vessels can also become blocked by an embolus or a thrombus thereby causing tissue damage downstream of the blockage.
A number of medical procedures have been developed to allow for the removal of plaque from vessel walls or to clear a channel through plaque, thrombus or clot to restore blood flow. For example, atherectomy or thrombectomy devices can be used to remove atheroma or thrombus. Vessel restrictions can also be treated with grafts that bypass the restrictions. Alternatively, balloon angioplasty and stenting procedures can be used to enlarge the lumen size of a vessel at an obstruction.
In a typical angioplasty procedure, a guide wire and guide catheter are inserted into a vessel of a patient. An inflatable balloon is then pushed through the guide catheter and advanced across a stenosis or blockage. Once positioned at the blockage, the balloon is inflated to dilate the blockage and open a flow channel through the partially blocked vessel region. One or more stents may also be placed across the dilated region or regions to reinforce the expanded vessel segment or to maintain dilatation of a vessel segment.
While some stenoses remain adherent to the vessel wall during treatment, others are more brittle, and may partially crack and fragment during treatment, allowing the fragments to flow downstream where they may block more distal and smaller vessels. Consequences of embolization include myocardial infarction, stroke, diminished renal function, and impairment of peripheral circulation possibly leading to pain and amputation.
Embolic protection devices have been developed to prevent the downstream travel of materials such as thrombi, grumous, emboli, and plaque fragments. Devices include occlusive devices and filters and may be deployed distal to a treatment site or proximal to a treatment site. Occlusive devices, for example distal inflatable balloon devices, can totally block fluid flow through the vessel. The material trapped by the inflatable devices can remain in place until removed using a method such as aspiration. Occlusive devices can also be deployed proximal to a treatment site and flow reversed or stopped at the treatment site. Following treatment emboli are carried by flow out of the vessel typically through a catheter and out of a patient. Filters can allow perfusing blood flow during the emboli capture process. The filters can be advanced downstream of a site to be treated and expanded to increase the filter area. Emboli, such as grumous or atheroma fragments, can be captured in the filter until the procedure is complete or the filter is occluded. When the capacity of the filter is reached, the filter may then be retracted and replaced.
Embolic protection devices can be delivered over guide wires and within guide catheters. The embolic protection methods are normally practiced ancillary to another medical procedure, for example angioplasty with stenting or atherectomy. The embolic protection procedure typically protects downstream regions from emboli resulting from practicing the therapeutic interventional procedure.